Air conditioning unit with reheat

ABSTRACT

An air-conditioning unit of the reheat-type particularly well suited for supplying conditioned air to a plurality of remotely located served zones has two condensers connected by parallel conduits to a reheat coil located in a hot deck of the unit and a refrigerant flow regulating valve responsive to served zone air parameters disposed in one of the parallel conduits for regulating the flow of refrigerant from one of the condensers to the reheat coil.

United States Patent [191 Kohlbeck Nov. 25, 1975 AIR CONDITIONING UNIT WITH REHEAT [75] Inventor: Orin J. Kohlbeck, Davenport, Iowa [73] Assignee'. American Air Filter Company, Inc.,

Louisville, Ky.

[22] Filed: Nov. 13, I974 [21] Appl. No.2 523,478

[52] U.S. Cl. 62/173; 62/90; 62/176; 62/208; 62/428 [51] Int. Cl. F25D 17/00 [58] Field of Search 62/90, 173, 176, 208, 428

[56] References Cited I UNITED STATES PATENTS 2,266,029 12/1941 Haines 62/173 2,702,456 2/1955 Ringquist 62/173 2,932,178 4/1960 Armstrong... 62/173 3,460,353 8/1969 Ogata et a1. 62/173 3,540,526 1 H1970 Hoaglund et al. 62/90 3,631,686 1/1972 Kautz 62/428 FOREIGN PATENTS OR APPLICATIONS 811,014 1/1937 France 62/90 Primary ExaminerWilliam J. Wye Attorney, Agent, or Firm-Jon C. Winger [57] ABSTRACT An air-conditioning unit of the reheat-type particularly well suited for supplying conditioned air to a plurality of remotely located served zones has two condensers connected by parallel conduits to a reheat coil located in a hot deck of the unit and a refrigerant flow regulating valve responsive to served zone air parameters disposed in one of the parallel conduits for regulating the flow of refrigerant from one of the condens ers to the reheat coil.

7 Claims, 4 Drawing Figures US. Patent Nov. 25, 1975 Sheet10f2 3,921,413

US Patent Nov. 25, 1975 Sheet 2 of2 3,921,413

AIR CONDITIONING UNIT WITH REHEAT BACKGROUND OF THE INVENTION The present invention relates to air conditioning units and more particularly to an air conditioning unit having a reheat coil to reheat air which has been previously cooled and dehumidified.

Airconditioning units having a reheat coil utilizing hot refrigerant as the reheating media are known. One such heretofore known unit, shown in U.S. Pat. NO. 3,631,686 issued on Jan. 4, 1972 to Franz P. Kautz, has two refrigerant condensers piped in parallel to a reheat coil located in a hot deck of the unit and a control valve in one of the pipes, which valve is responsive to the temperature of an air stream in heat exchange relationship with the reheat coil so that as the air stream temperature leaving the reheat coil goes below a predetermined temperature, the control valve closes causing one of the condensers to flood with liquid refrigerant, thus, decreasing the effectiveness of the other condenser. Because the other condenser is not capable of condensing the entire volume of gaseous refrigerant it now receives from the compressor, it discharges a mixture of liquid and gaseous refrigerant to the reheat thereby forcing the reheat coil to function as a condenser.

Idealy, a reheat event should bbe initiated or controlled by the actual air conditions or parameters prevailing within the zones served by the air conditioning unit. These zone air parameters comprise solar heat gain or loss through windows, roofs, ceilings and doors; internal heat gain from people and euipment within the served zone; and heat gain or loss from infiltration of outside air; another air parameter is, of course, humidity. Additional factors which effect the amount of heat to be supplied by a heating source to a zone include a compensating amount of heat for the heat lost from the heating air stream as it is transmitted through the ducts to the zone and for any ventilating air introduced into the served zone.

The above-described prior art air-conditioning unit ignores these prefailing conditions within the served zone and instead controls or initiates the reheat event in response to an arbitrary predetermined temperature setting at the reheat coil which is located in a hot deck of the unit remote from the served zones.

SUMMARY OF THE INVENTION The present invention recognizes the need for initiating and controlling a reheat event by the actual prevailing air conditions within the served zones and provides an air-conditioning unit of the reheat-type which has a refrigerant regulating valve responsive to the conditions of the air within the served zones for controlling the flow of refrigerant from a condenser to a reheat coil. More particularly, the present invention provides an air-conditioning unit of the reheat-type for supplying conditioned air to at least one remotely located served space, the air-conditioning unit comprising:

a hot deck portion;

a cold deck portion;

means for selectively routing at least a portion of an air stream to be conditioned through the hot deck portion;

means for selectively routing at least a portion of an air stream to be conditioned through the cold deck por tIOII;

a reheat coil in the hot deck portion for selectively reheating the air stream flowing through the hot deck portion;

at least two condensers in parallel refrigerant flow communication with the reheat coil;

at least one compressor having its pressure side in refrigerant flow communication with the condensers;

an evaporator disposed upstream of the reheat coil for selectively cooling an air stream to be routed into the hot deck portion and the cold deck portion, the evaporator being in refrigerant flow communication with the reheat coil and with the suction side of the compressor;

a refrigerant flow regulating valve for controlling the flow of refrigerant between at least one of the condensers and the reheat coil;

a served zone air condition sensor disposed within each of the served zones, the sensor being immediately responsive to the conditions of the air within the served zones for actuating the regulating valve to restrict the flow of refrigerant from one of the condensers to the reheat coil when the served zone air conditions deviate from a desired condition.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the present invention will be had upon reference to the accompanying drawings where like numerals refer to like parts throughout the several views and wherein:

FIG. I is a schematic representation of an air conditioning unit utilizing the present invention;

FIG. 2 illustrates one operating mode of the air conditioning unit of FIG. 1;

FIG. 3 illustrates another operating mode of the air conditioning unit of FIG. 1; and.

FIG. 4 illustrates yet another operating mode of the air conditioning unit of FIG. 1

DESCRIPTION OF THE PREFERRED EMBODIMENT The term air conditioning as it is used herein includes heating as well as cooling the air to be treated.

Referring to FIG. 1, there is illustrated an air conditioning unit, generally denoted as the numeral 10, which is particularly well suited for supplying conditioned air to a plurality of remotely located served spaces or zones (not shown). Usually, an air conditioning unit of the type illustrated is mounted on the roof of a building and is, therefore, referred to in industry as a roof-mounted multi-zone unit.

Generally, the multi-zone air-conditioning unit 10 comprises a housing 12; a refrigeration system, generally denoted as the numeral 14, disposed within the housing 12; and a refrigerant control system, generally denoted as the numeral 16.

The housing 12 comprises a hot deck portion 20 through which heated air flows, and a cold deck portion 22 through which cooled air flows. Furthermore, a plurality of hot deck zone dampers 24 are disposed at the outlet from the hot deck 20 and a plurality of cold deck zone dampers 26 are disposed at the outlet from the cold deck 22 to selectively route an air stream through the decks. The number of hot deck dampers 24 and number of cold deck dampers 26 are dictated by, and are equal in number to the number of zones served by the unit 10. Furthermore, the hot deck and cold deck dampers are constructed in sets so that each served zone has its own set of hot and cold deck dampers for selectively controlling the amounts of treated air to be received from the hot and cold decks to satisfy the demands of that zone. In addition. the dampers 24 and 26 are coordinated so that as the hot deck dampers 24 ofa set move toward an open position the cold deck dampers 26 of that set move toward a closed position. and visa versa. When the hot deck dampers of a set are completely open. the cold deck dampers of that set are completely closed. and likewise. when the cold deck dampers are completely open the hot deck dampers are completely closed. Between these extreme damper positions. both the hot deck and cold deck dampers are partially open to a varying extent to allow a coordinated air flow from both the hot deck and cold deck.

The refrigerant system 14 comprises at least two condensers 28 and 30, a compressor 32, a reheat coil 34 disposed in the hot deck portion 20, and an evaporator coil 36 disposed to cool an air stream flowing to both the hot deck and cold deck 22. The refrigerant system 14 further includes parallel refrigerant conduits 38 and 40 connecting the condensers 28 and 30, respectively, to the pressure side of the compressor 32; parallel refrigerant conduits 42 and 44 connecting the con densers 28 and 30, respectively, via a conduit 45 to the reheat coil 34; a refrigerant conduit 46 interconnecting the reheat coil 34 and the evaporator 36; an expansion valve 49 in the conduit 46 between the reheat coil 34 and evaporator 36; and a refrigeration conduit 50 interconnecting the evaporator 36 and suction side of the compressor 32 forming a closed loop refrigeration circuit. Various accessories may be placed in the various refrigerant conduits. such as a filter dryer in the conduit 46 and an accumulator in the conduit 50 as well as at least one fan 51 disposed over the condensers. A re frigerant flow regulating valve 52 may be disposed in either one of the parallel refrigerant conduits 38 or 40. but for the sake of clarity of discussion. it will be assumed to be installed in the conduit 40. The valve 52 is actuated by a solenoid 54 to restrict the flow of refrigerant from the condenser 30. While the valve 52 is illustrated as being a two-way valve which is either open to allow unrestricted refrigerant flow or closed to completely block the refrigerant flow through the refrigerant circuit. it instead could be a metering-type valve for modulating the volume rate of flow of refrigerant.

The refrigerant control system 16 comprises a regulating valve control means. such as a served zone air condition sensor 56 located in each of the served zones.

Each sensor 56 is operatively connected through. for

example. a system controller 58 to the solenoid 54 to actuate the valve 52 to a refrigerant flow restricting position when conditions within it served zone require reheat. In addition, an outdoor air temperature sensor 60 is operatively connected to the system controller 58 to allow a served zone sensor 56 to actuate the valve 52 only when the outdoor air temperature is below a predetermined temperature. ln pratice. this temperature has been determined to be approximately Fahreheit. If the valve 52 where actuated to a flow restricting position when the outdoor air temperature is above 70Fahrenheit, thus, reducing the effective condensing area. the compressor head pressure would increase to a level which could damage the compressor.

A separate damper actuator 62 is operatively connected to each set of hot and cold deck dampers 24 and 26, and each served zone sensor 56 is operatively connected. through the system controller 58, to the zone 4 actuator 62 operating the dampers controlling the air flow into the zone in which it is disposed.

FIG. 2 best illustrates the conditions prevailing within the air-conditioning unit 10 when all of the served zone sensors 56 are calling for percent cool air from the unit 10. The refrigerant flow regulating valve 52 is open allowing unrestricted refrigerant flow through the refrigerant system 14 under the influence of the compressor 14: all of the hot deck dampers 24 are closed and all of the cold deck dampers 26 are open.

Refrigerant vapor is conveyed through conduits 38 and 40 from the compressor 32 to the condensers 28 and 30 (see arrows A). The refrigerant vapor is essentially completely condensed in the condensers. The condensed refrigerant exits the condensers 28 and 30 through conduits 42 and 44 and is conveyed to the reheat coil 34 through conduit 45 (see arrows B).

The condensed refrigerant exits the reheat coil 34 through the conduit 46 (see arrows C to the evaporator 36 and from the evaporator through conduit 50 back to the compressor 32. An air stream to be treated passes in heat exchange relationship through the evaporator 36 whereat it is cooled (see arrow D"). Because in the cooling mode the hot deck dampers 24 are fully closed and the cold deck dampers 26 are fully open. the entire air stream cooled by the evaporator 36 is routed through the cold deck portion 22 (see arrow E") and exits through the open cold deck dampers 26 (see arrow F). to be distributed to the served zones. Because virtually all of the refrigerant has been condensed in the condensers 20 and 22 prior to being conveyed to the reheat coil 34 and because virtually no air is routed through the hot deck portion 20, the reheat coil 34 is redundant in the full cooling mode.

FIG. 3 illustrates the prevailing conditions within the air-conditioning unit 10 when at least one of the served zone sensors 56 is calling for some amount of heat less than 100 percent of the heat capable of being supplied by the reheat coil 34. Under this operating mode, the served zone sensor 56 calling for the most heat closes the regulating valve 52 restricting refrigerant flow from the condenser 30 to the reheat coil thus, causing the entire volume of refrigerant vapor to flow into the condenser 28 from the compressor 32 (see arrows G). The condenser 28 does not have sufficient capacity to condense this amount of vapor refrigerant and, therefore, discharges a mixture of refrigerant vapor and hot refrigerant fluid through conduits 38 and 45 (see arrows H) to the reheat coil 34. In this manner, the re heat coil 34 is forced to function as a condenser to condense the vapor portion of the refrigerant to heat an air stream flowing through the hot deck. The now condensed refrigerant passes from the reheat coil 34 through conduit 46 to the evaporator 36 (see arrow l") and from the evaporator through the conduit 50 back to the compressor 32 (see arrow .l). Concurrently. the served zone air condition sensor 56 causes the hot deck dampers 24 to partially open and the cold deck dampers 26 to partially close to route a portion of the air stream cooled by evaporator 36 (see arrows K") to flow through the hot deck portion 20 and into heat exchange relationship with the reheat coil (see arrows L") where the air stream is reheated and another portion of the air stream through the cold deck portion 22 (see arrow M). The reheated air stream from the hot deck portion and cool air stream from the cold deck exit through the hot and cold deck dampers, respectively, to be mixed downstream of the unit 10 and distributed to the served zone calling for heat. The hot deck dampers controlling the air flow from the unit to the served zones which are not calling for heat remain closed and the cold deck dampers remain open.

FIG. 4 best illustrates the prevailing conditions within the air-conditioning unit 10 when 100 percent reheated air is demanded by at least one of the served zone air condition sensors. The flow regulation valve 52 is closed by means of the sensor 56 actuating the solenoid 54, thus, causing all of the refrigerant vapor to flow into the condenser 28 (see arrows N). As hereinabove discussed, the condenser 28 is incapable of condensing all of the refrigerant vapor and, therefore, discharges a mixture of refrigerant vapor and liquid refrigerant through the conduits 38 and to the reheat coil 34 (see arrows 0) thereby forcing the reheat coil 34 to function as a condenser in place of the blocked condenser 30. The now completely condensed refrigerant passes from the reheat coil 34 through the conduit 46 to the evaporator 36 (see arrow P") and from the evaporator through the conduit 50 back to the compressor (see arrow Q). Concurrently, the hot deck dampers 24 controlling the air flow to the zones calling for 100 percent reheat are completely opened and the cold deck dampers comletely closed to route all of the air cooled by the evaporator 36 (see arrows R) through the hot deck portion 20 and into heat exchange relationship with the reheat coil 34 (see arrows S). The reheated air stream exits the hot deck through the hot deck dampers 24 to be distributed to the served Zone calling for 100 percent reheat. The hot deck dampers controlling the air flow from the unit 10 to the served zones which may concurrently be calling for some heat less than 100 percent reheat are partially open and the cold deck dampers are also partially open to route a mixture of hot and cold air to those served zones. The hot deck dampers controlling the air flow from the unit 10 to any served zones which are not calling for any heat remain closed and the cold deck deampers remain open.

Unlike the prior art air conditioning unit wherein a refrigerant flow control valve is actuated by a thermostat sensor in the hot deck sensing only the air stream temperature leaving the re heat coil such that at an arbitrary predetermined temperature setting the thermostatic sensor actuates a refrigerant control valve, the served zone air condition sensor 56 of the present invention, which may be either a thermostat or humidistat, is both immediately responsive to the actual air conditions existing within a served zone and is adjustable so that the set point at which the regulator valve 52 is closed can be varied to compensate for varying air conditions actually existing with the served zone at any particular point in time.

The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are be understood therefrom for modifications will become obvious to those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention or scope of the appended claims.

What is claimed is:

1. An air-conditioning unit of the reheat-type for supplying conditioned air to at least one served zone. said air conditioning unit comprising:

a hot deck portion;

a cold deck portion;

means for selectively routingat least a portion of an air stream to be conditioned through said hot deck portion to each servedzone;

means for selectively routing at least aportion of an air stream to be conditioned through said cold deck portion to each served zone;

a reheat coil disposed in said hot deck for selectively reheating the air stream flowing through said hot deck portion;

at least two condensers having their outlets in parallel refrigerant flow communication with the inlet of said reheat coil;

at least one compressor having its pressure side in refrigerant flow communication with the inlet of said condensers;

an evaporator disposed upstream of said reheat coil for selectively cooling an air stream flowing into said hot deck portion and said cold deck portion, the inlet of said evaporator being in refrigerant flow communication with the outlet of said reheat coil and the outlet of said evaporator being in refrigerant flow communication with the suction side of said compressor;

a refrigerant flow regulating valve for controlling the flow of refrigerant between at least one of said condensers and said reheat coil; and.

a served zone air condition sensor disposed within each served zone, each of said sensors being immediately responsive to the conditions of the air within the served zone for actuating said regulating valve to restrict the flow of refrigerant from one of said condensers to said reheat coil when the served zone air conditions within a served zone deviate from a desired condition.

2. The air-conditioning unit defined in claim 1, further comprising an outdoor air temperature sensor for allowing a served zone air condition sensor to actuate said regulating valve only when the outdoor air temperature is below a predetermined temperature.

3. The air-conditioning unit defined in claim 2, wherein said predetermined temperature is approximately Fahrenheit.

4. The air-conditioning unit defined in claim 1, wherein:

said served zone air condition is the served zone air temperature; and,

said served zone air condition sensor is a thermostat.

5. The air-conditioning unit defined in claim 1, wherein:

said served zone air condition is the served zone air humidity; and,

said served zone air condition sensor is a humidistat.

6. The air-conditioning unit defined in claim 1, wherein:

said hot deck portion routing means comprise movable dampers for selectively controlling the flow of air through said hot deck portion to each served zone; and,

said cold deck portion routing means comprise movable dampers for selectively controlling the flow of air through said cold deck portion to each served zone.

7. The air conditioning unit defined in claim 6,

wherein:

said served zone air condition sensor in each served zone causes said hot deck portion dampers controlling the air flow to that served zone to move between open and closed positions in response to trolling the air flow to that served zone to move beserved zone air conditions; and. tween open and closed positions in response to said served zone air condition sensor in each served served zone air conditions.

zone causes said cold deck portion dampers conq 

1. An air-conditioning unit of the reheat-type for supplying conditioned air to at least one served zone, said air conditioning unit comprising: a hot deck portion; a cold deck portion; means for selectively routing at least a portion of an air stream to be conditioned through said hot deck portion to each served zone; means for selectively routing at least a portion of an air stream to be conditioned through said cold deck portion to each served zone; a reheat coil disposed in said hot deck for selectively reheating the air stream flowing through said hot deck portion; at least two condensers having their outlets in parallel refrigerant flow communication with the inlet of said reheat coil; at least one compressor having its pressure side in refrigerant flow communication with the inlet of said condensers; an evaporator disposed upstream of said reheat coil for selectively cooling an air stream flowing into said hot deck portion and said cold deck portion, the inlet of said evaporator being in refrigerant flow communication with the outlet of said reheat coil and the outlet of said evaporator being in refrigerant flow communication with the suction side of said compressor; a refrigerant flow regulating valve for controlling the flow of refrigerant between at least one of said condensers and said reheat coil; and, a served zone air condition sensor disposed within each served zone, each of said sensors being immediately responsive to the conditions of the air within the served zone for actuating said regulating valve to restrict the flow of refrigerant from one of said condensers to said reheat coil when the served zone air conditions within a served zone deviate from a desired condition.
 2. The air-conditioning unit defined in claim 1, further comprising an outdoor air temperature sensor for allowing a served zone air condition sensor tO actuate said regulating valve only when the outdoor air temperature is below a predetermined temperature.
 3. The air-conditioning unit defined in claim 2, wherein said predetermined temperature is approximately 70* Fahrenheit.
 4. The air-conditioning unit defined in claim 1, wherein: said served zone air condition is the served zone air temperature; and, said served zone air condition sensor is a thermostat.
 5. The air-conditioning unit defined in claim 1, wherein: said served zone air condition is the served zone air humidity; and, said served zone air condition sensor is a humidistat.
 6. The air-conditioning unit defined in claim 1, wherein: said hot deck portion routing means comprise movable dampers for selectively controlling the flow of air through said hot deck portion to each served zone; and, said cold deck portion routing means comprise movable dampers for selectively controlling the flow of air through said cold deck portion to each served zone.
 7. The air conditioning unit defined in claim 6, wherein: said served zone air condition sensor in each served zone causes said hot deck portion dampers controlling the air flow to that served zone to move between open and closed positions in response to served zone air conditions; and, said served zone air condition sensor in each served zone causes said cold deck portion dampers controlling the air flow to that served zone to move between open and closed positions in response to served zone air conditions. 